Field of the Invention
The present invention relates to an access selection method.
Related Art
In 3GPP in which technical standards for mobile communication systems are established, in order to handle 4th generation communication and several related forums and new technologies, research on Long Term Evolution/System Architecture Evolution (LTE/SAE) technology has started as part of efforts to optimize and improve the performance of 3GPP technologies from the end of the year 2004.
SAE that is progressed around 3GPP SA WG2 is a research into network technology to determine a structure of a network with an LTE work of a 3GPP TSG RAN and support mobility between model networks and one of key standardization issues of the 3GPP. This is a work for developing a 3GPP system to a system that supports various wireless access technologies based on an IP and the work has been progressed for the purpose of an optimized packet based system that minimizes a transmission delay with a further improved data transmission capability.
An Evolved Packet System (EPS) higher level reference model defined in 3GPP SA WG2 includes a non-roaming case and roaming cases having various scenarios, and for details therefor, reference can be made to 3GPP standard documents TS 23.401 and TS 23.402. A network configuration of FIG. 1 has been briefly reconfigured from the EPS higher level reference model.
FIG. 1 is a Structural Diagram of an Evolved Mobile Communication Network.
One of largest features of the network structure of FIG. 1 is based on a 2 tier model of eNodeB of an evolved UTRAN and a gateway of a core network and although accurately coincides with each other, the eNodeB 20 has functions of NodeB and RNC of an existing UMTS system and the gateway has an SGSN/GGSN function of the existing system.
Another key feature is that a control plane and a user plane between an access network and the core network are exchanged to different interfaces. In the existing UMTS system, one Iu interface exists between an RNC and an SGSN, while a mobility management entity (MME) 51 that undertakes processing of a control signal has a structure separated from a gateway (GW), and as a result, two interfaces of S1-MME and S1-U are respectively used. The GW includes a serving-gateway (hereinafter, referred to as ‘S-GW’) 52 and a packet data network gateway (hereinafter, referred to as ‘PDN-GW’ or ‘P-GW’) 53.
FIG. 2a Shows an Example of an as IP Flow Mobility and Seamless Offload (IFOM) Technique, and FIG. 2b Shows an Example of an Multi Access PDN Connectivity (MAPCON) Technique.
Recently, with an explosive increase in data, there is an increase in a congestion of a core network of a mobile communication operator. As a way of solving this problem, there is an attempt to offload data of a user equipment (UE) to a wired network without via the core network.
As a result of such discussion, a technique such as IP flow mobility and seamless offload (IFOM), none-seamless WLAN offloading (NSWO), multi access PDN connectivity (MAPCON), or the like has been proposed to support a multiple radio access. The IFOM technique is a technique of transmitting data by using a 3GPP access and a Wi-Fi access aggregated with one PDN or P-GW. Further, the MAPCON technique is a technique of transmitting data by using each of the 3GPP access and the Wi-Fi access through respective PDN connections.
As shown in FIG. 2a, the IFOM provides an identical PDN connection simultaneously through different several accesses. The IFOM provides a seamless offload to a WLAN. In addition, the IFOM provides a delivery of an IP flow of one identical PDN connection from one access to another access.
In addition, referring to FIG. 2a, the non-seamless WLAN offloading (NSWO) technique provides a non-seamless offload to the Wi-Fi access, that is, an offload in which traffic may be suspended.
Meanwhile, as shown in FIG. 2b, the MAPCON technique is to establish several PDN connections, simply, IP flows, to different APNs through different access systems.
According to the MAPCON technique, a UE 10 may create a new PDN connection on an access which is not used previously. Alternatively, the UE 10 may create a new PDN connection on one access selected from several accesses used previously. Alternatively, the UE 10 may move the entirety or part of all PDN connections, which have already been connected, to another access.
FIG. 3 Shows an Access Network Discovery and Selection Function (ANDSF), and FIG. 4 Shows an Exemplary Structure of an Inter-System Routing Policy (ISRP) Provided by the ANDSF.
As described above, in order to offload traffic to a normal data communication network, an operator may provide a policy to a UE, and the UE may offload its data to a wireless LAN according to the policy.
For provisioning of such a policy to the UE, an access network discovery and selection function (ADNSF) based on 3GPP is improved to be capable of providing a policy related to the wireless LAN.
As shown in FIG. 3, an ANDSF 61 may exist in a home public land mobile network (HPLMN) of a UE 10.
As shown in FIG. 4, the ANDSF provides an inter-system routing policy (ISRP). The ISRP implies a routing policy for data traffic between a 3GPP access system and a non-3GPP access system.
In this case, as described above, IFOM enables a plurality of PDN connections through several accesses by using the same APN. In this case, the ISRP provides an IP flow-based rule, i.e., ForFlowBased.
In addition, for the aforementioned NSWO, the ANDSF may provide a policy for a non-seamless offload, i.e., ForNonSeamlessOffload, to the ISRP.
On the other hand, recently, in 3GPP, there is on-going research on an inter APN routing policy (IARP) for selecting an IP interface on the basis of the APN under the name of operator policies for IP interface selection (OPIIS). In the IARP, a priority is designated for several APNs and NSWOs so that an IP interface having a top priority can be selected among IP interfaces available for a specific IP flow.
However, a collision problem may occur since rules are different from each other between the existing ISRP and the newly discussed IARP. Due to such a collision, a UE eventually cannot select an optimal interface.